The present invention relates to an image processing system, projector, program, information storage medium and image processing method which can correct a distortion in a projected image such as keystone distortion and rotation.
Various kinds of techniques for correcting a distortion in an image projected by a projector such as so-called keystone distortion have been proposed.
For example, a technique for detecting an inclination in a projector and automatically correcting a vertical distortion is known in the art.
However, such a technique cannot allow a user to correct a horizontal distortion.
For such a reason, the user must use a technique of manually correcting the horizontal distortion by operating a correction switch in a remote controller while viewing an image to be corrected.
However, such a manual operation takes time. In addition, it is difficult to perform an adequate correction in the manual manner.
In view of such a problem, for example, Japanese Patent Laid-Open Application No. 2000-241874 proposes a system in which a projection plane is imaged or taken by means of a camera and the opposed sides in the projection area is compared in length with each other to sense a distortion which is in turn corrected based on the sensed result.
However, the camera used in this Japanese Patent Laid-Open Application is included in the main projector body so that the optical axis of the camera is substantially identical with that of a lens. Thus, the projection area shown by the taken image is always of substantially rectangular shape. It is therefore difficult to compare the length of the opposed sides in the projection area based on the taken image.